I 



54 II. BIOSYNTHESIS 



over, Artom et oZ. 288.245, 258 reported that the specific activity of kidney 

 phospholipid is lower than that of the liver and small intestine during 

 the early period following the administration of P*^. On the other hand, 

 Fishier and associates, in unpublished observations cited by Chaikoff,^^^ 

 reported that the deposition of P^^ in the kidney phospholipids of the dog 

 was less than that in the liver, but more than the amount in the small 

 intestine at six hours. After ninety-eight hours, the concentrations in all 

 these tissues were essentially the same. 



The ability of the kidney to effect the synthesis locally rather than merely 

 to withdraw it from the blood has been amply proved. Thus, the kidney 

 of the hepatectomized dog was found by Fishier et al."^^^ to contain newly 

 formed phospholipid, despite the fact that none was present in the plasma; 

 the quantities of radiophospholipid were similar in the kidneys of normal 

 and of liverless dogs. 



However, the most cogent argument for the thesis that the kidney cells 

 themselves possess the ability to synthesize phospholipid is the fact that 

 kidney slices, like liver slices, can incorporate labeled phosphate into the 

 phospholipid in the presence of oxygen, although this capacity is reduced to 

 10% of the normal value when the kidney shces are kept under nitrogen. 

 However, unlike liver homogenates,^^^ those prepared from kidney are still 

 able to form new phospholipid.^*^ 



d. Muscle. The rate of synthesis of phospholipids in skeletal muscle, 

 as determined in experiments in which P*^ was used as a tracer, is slower 

 than that exhibited by small intestine, liver, or kidney tissue. ^^^-^^'-^^^'^^^ 

 The slow rate of synthesis of phospholipid under these conditions may be 

 related to the rate of entrance of inorganic phosphorus into the muscle 

 ggjj 237,260,261 Euteumau and co-workers^*^ reported that the phosphohpid 

 P^^ content of leg and breast muscle of the bird was the same six and twelve 

 hours after the injection of P^^, but that cardiac muscle incorporated more 

 P82 than did other types of muscle. Bloor and Snider-*^ noted that the 

 phospholipid content of muscle paralleled the activity of the muscle, but 

 the reason for this is unexplained. Artom^*' and Friedlander et al.^^* ob- 

 served that administered P*^ is deposited in muscle phospholipids at an in- 



258 C. Artom, G. Sarzana, C. Perrier, M. Santangelo, and E. Segre, Nature, 139, 836- 

 837 (1937). 



269 G. Hevesy, Ann. Rev. Biochem., 9, 641-662 (1940). 



260 J. F. Manery and W. F. Bale, A?n. J. Physiol., 132, 215-231 (1941). 



2" G. Hevesy and O. Rebbe, Acta Physiol. Scand., 1, 171-182 (1940). 



262 W. R. Bloor and R. H. Snider, J. Biol. Chem., 107, 459-470 (1934). 



2" C. Artom, J. Biol. Chem., 139, 953-961 (1941). 



2" H. D. Friedlander, I. Perlman, and I. L. Chaikoff, Am. J. Physiol, 132, 24-31 (1941). 



